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AMG C63 S Turbo Rattle on Deceleration - Wastegate Issue?

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Mark S. · rep 0 · May 22, 4:13 AM · 1 replies · solved · Question

Vehicle: 2019 Mercedes-AMG C63 S Coupe

Hey everyone,

I've got a 2019 Mercedes-AMG C63 S Coupe (W205) with the M177 engine, and I've started noticing a distinct rattling sound coming from the engine bay. It's most prominent when I lift off the throttle, especially after accelerating, or sometimes on a cold start. It sounds like a metallic rattle, almost like loose heat shields, but it seems to be coming from the turbocharger area.

I've read online that this could be related to the turbocharger wastegate actuators or the wastegate itself. My car has about 40,000 miles on it. Has anyone else with an M177 engine experienced this? Is this a common issue, and what was the fix? I'm concerned about potential turbo damage.

Any advice or shared experiences would be greatly appreciated!

Thanks, Mark

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:13 AM

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ClearTheCode admin answer:

The rattling sound you're describing on your 2019 Mercedes-AMG C63 S with the M177 engine is a well-documented issue, and you're likely correct in suspecting the turbocharger wastegate system.

Here's a breakdown:

  1. Understanding the Problem:

    • Causes: The M177 engine uses twin turbochargers, each with an electronically controlled wastegate. Over time, the bushings or pivots in the wastegate actuator arm or the wastegate flap itself can wear, leading to excessive play. This play causes the wastegate components to rattle, especially when there's no exhaust gas pressure holding them tight (e.g., on deceleration or at idle).
    • Symptoms: A metallic rattling sound from the turbo area, often noticeable on cold start, deceleration, or when revving the engine slightly and letting off. In severe cases, it can lead to boost control issues, though the rattle usually appears before performance is significantly affected.

  2. Diagnosis:

    • A technician will typically use a stethoscope to pinpoint the source of the rattle. They may also physically inspect the wastegate actuator arms for excessive play. Sometimes, removing the downpipes allows for a direct visual inspection of the wastegate flaps.
    • While there might not be a specific OBD-II code for a wastegate rattle, prolonged issues could lead to boost pressure codes (e.g., P0299 - Turbocharger/Supercharger Underboost) if the wastegate isn't sealing properly.

  3. Potential Solutions:

    • Wastegate Actuator Replacement: If the play is in the actuator arm, sometimes just replacing the actuator can resolve it.
    • Turbocharger Replacement: Unfortunately, in many cases, the wear is within the turbocharger housing itself (where the wastegate flap pivots). Mercedes-Benz often recommends replacing the entire turbocharger assembly, as the wastegate components are not typically serviceable separately.

When to See a Shop: It's crucial to have your AMG C63 S inspected by a Mercedes-Benz dealership or an AMG-certified specialist. They have the expertise and specialized tools to accurately diagnose the source of the rattle. While a rattle might seem minor, if it's indeed a wastegate issue, it can eventually lead to boost control problems and potentially more significant turbocharger damage if left unaddressed. Since your car is a 2019, check if it's still under warranty or if there are any service campaigns related to this issue.

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